Summary: Randomization does not Reduce
the Average Delay in Parallel Packet Switches
Hagit Attiya
Department of Computer Science
Technion
hagit@cs.technion.ac.il
David Hay
Department of Computer Science
Technion
hdavid@cs.technion.ac.il
ABSTRACT
Switching cells in parallel is a common approach to build
switches with very high external line rate and a large num-
ber of ports. A prime example is the parallel packet switch
(in short, PPS) in which a demultiplexing algorithm sends
cells, arriving at rate R on N input-ports, through one of K
intermediate slower switches, operating at rate r < R.
This paper presents lower bounds on the average queuing
delay introduced by the PPS relative to an optimal work-
conserving FCFS switch, for demultiplexing algorithms that